This invention relates to a process for sterilizing and cleaning the head space of an aseptic filling system for a pack provided with a spout comprising an outer tearable membrane. The invention also relates to a device for carrying out this process.
Aseptic filling systems are already known in which a device for sterilizing and cleaning the system after filling is provided at the base of the filling head. European patent application 271 242, for example, relates to one such device.
Using an aseptic filling system, a pre-sterilized pack is filled cold and, after filling, the body and walls of the head space are cooled through the presence of the cold product. After the introduction of another pack, the head space and the surface of the pack resting against it have to be re-sterilized. Now, sterilization is carried out with saturated steam at a temperature in the range from 140.degree. to 150.degree. C. If it were desired to eliminate all the germs at that temperature, the sterilization time would have to be of the order of 3 to 10 minutes. The reason for this is that the saturated steam is unable to bring the cold and continually cooled walls of the head space to the necessary temperature for inactivating the heat-stable germs. These walls actually remain at a temperature of the order of 120.degree. to 125.degree. C. Elimination of the heat-stable germs cannot be guaranteed at that temperature. In any event, it would be totally unthinkable in economic terms to carry out sterilization for such a long period. Sterilization has to be completed in less than 10 seconds.
In addition, if the head space were heated at an excessively high temperature for too long, the outer tearable membrane and the spout would soften and deform, which would be unacceptable for the rest of the process. On the other hand, in the patent application cited above, the steam inlet valve and the steam outlet and emptying valve are arranged opposite one another. Now, experience has shown that an arrangement such as this does not enable all the residues of product in the spout to be fully removed in an acceptable time during cleaning or rinsing of the interior of the spout after filling.